A "massive bilateral trade deal" between Britain and America is unlikely to be possible if Theresa May's Brexit deal succeeds, the US ambassador to the UK has claimed.
Woody Johnson said US President Donald Trump would look positively at an outcome which enabled America to strike major trade agreements with the UK.
But he cautioned that if the Prime Minister's Withdrawal Agreement were to succeed, then negotiating a "quick" and "massive" trade deal between the US and UK "doesn't look like it would be possible".
Mr Johnson told BBC Radio 4's Today programme: "He (Mr Trump) is looking forward to and hoping that the environment will lead to the ability of the US to do a quick, very massive bilateral trade deal that could be the precursor of future trade deals with other countries around the world for Great Britain that will really take you way, way into an exciting future.
"We are still going through the stages of deciding where exactly the country is going. If it goes in a way that allows these kind of agreements to occur then I think that will be very positive in the president's eyes."
But asked if such a deal would be possible if Mrs May's Withdrawal Agreement is agreed, he said: "It doesn't look like it would be possible."
Mr Trump has previously said Mrs May's Brexit deal "sounds like a great deal for the EU".
Mr Johnson also told the programme he thought it was "probably true" that Parliament is not providing a clear sense of where the country is going.
He said: "You can see the frustration in the Members of Parliament in trying to navigate what the people wanted when they voted on the referendum."
And he said he detected a "defeatism" about Brexit, saying: "If you look back and you just try to project the past into the present and the future, it's going to be bleak.
"But you're leaving out the great thing that Britain has to offer, and that is all of the people and all of their efforts and their ability to solve problems. And if you factor that in, I think the future is extremely positive and extremely bright."
On the postponed, controversial state visit to the UK, Mr Johnson said he thought Mr Trump "would be in favour of it".
Asked whether May 2019 would be good date, the ambassador said it would be a "good time" but noted that it "has to be on both sides".